Water-soluble polymers are preferable for use in a detergent builder, and for example, unsaturated carboxylic acid-based (co)polymers such as acrylic acid, methacrylic acid, α-hydroxyacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid or citraconic acid have conventionally used as the water-soluble polymer.
In recent years, improvement and research in such (co)polymers are actively made for the purpose of improving performances in various uses of detergent builders.
In particular, where a detergent builder based on an unsaturated carboxylic acid-based polymer or a modified product thereof as described in JP-A 2002-12627 is used as a powder detergent, its performance could be exhibited in a relatively high level.
However, a detergent builder comprising the above-described conventional unsaturated carboxylic acid-based (co)polymer had disadvantages that the (co)polymer has very poor compatibility with a surfactant, and as a result, such is not suitable for use as a liquid detergent.
Further, citric acid has been used as a chelating agent in a liquid detergent. However, citric acid does not have clay (dirt) dispersibility, and therefore, a dispersant has been desired to improve detergency.
Polyacrylic acid (salt) is used as a dispersant in a liquid detergent, but this is not compatible with a liquid detergent containing a surfactant in high concentration.